I had sex yesterday, it was my 3rd or 4th time but I haven't done sex for 2 years n now I'm bleeding since morning n it's like periods not spotting. I think I had my last period on 5th of this month. and while we had sex he ejaculated outside the vagina on my belly. so, why am I bleeding and what are the chances of pregnancy? and what can I do to prevent pregnancy?
Bleeding the day after first sex in 2 years is hardly surprising; things may have tightened up in there. You were close enough to ovulation (CD14=Mar19th) that sperm could last until then. Stories of pulling out to ejaculate on your belly leave open the possibility that the first squirt could have been inside.
The chance of pregnancy from a well timed encounter is never more than 30%. If you believe zero sperm escaped inside the chance is much reduced. I think in your situation I would be inclined to take emergency contraception ASAP. It will mess with the timing of your next period. Please buy your own condoms when you get the PlanB and insist on them being used correctly for every penetration.